General/Distribution:
A genus of about 400 species distributed mainly in the tropical and subtropical regions of America, Africa and Asia. A few species are found in Australia, North America and only two in Europe (Webb in Tutin et al., Fl. Eur. 5: 117. 1980). Represented in Pakistan by a single species.

Usually glabrous, annual herbs with whitish fibrous roots. Leaves linear. Inflorescence capitate, subtended by an involucre of bracts. Involucral bracts ± orbicular to narrowly lanceolate, longer or shorter than the inflorescence. Perianth of 2 whorls, each whorl 2-3-merous. Segments of the outer whorl of male flowers free or basally united, inner whorl forming a tube, with a black gland at the apex of each segment. Segments 4-6, a rudimentary gynoecium sometimes present. Segments of the outer whorl in female flowers free or connate, inner segments free, with an apical black gland, or sometimes the segments lacking. Style absent. Seeds with a striped surface.